A parallel hard-type hybrid system has an operation mode in which power is transmitted by driving an engine and a motor at a synchronous speed by locking up the engine and the motor to each other through lock-up of the engine clutch, and an operation mode (EV mode) in which the engine clutch is opened and the motor transmits power with the engine stopped.
When a high voltage that is supposed to be applied to an inverter is suddenly interrupted due to an occurrence of abnormality in the vehicle during the operation mode (EV mode), in which the vehicle is driven only by the motor with the engine turned off, the engine needs to be driven for limp-home driving of the vehicle as a fail-safe strategy. In other words, a hybrid starter generator (HSG) serves to start the engine by using a pulley and a belt connected to the engine in a normal situation, but when an input of a high voltage is interrupted, the HSG cannot be normally driven. In this case, in conventional cases, the engine is started by attempting lock-up through the motor kept rotating at a high speed, the stationary engine and slip control of the engine clutch. At this time, vibration (jerk) occurs in the vehicle as the engine in a stationary state is joined to the motor rotating at a high speed to start the engine.
Therefore, there is a need for solutions for minimizing vibration of the vehicle in joining the motor to the engine before entering the limp-home mode and for enhancing operability in a situation where a high voltage to the inverter is interrupted due to abnormal operation of the high voltage system of the hybrid vehicle.
The foregoing description of the background art is merely intended to promote an understanding of the background of the present invention and is not to be construed as suggesting that the present invention corresponds to a conventional technology already known to those skilled in the art.